"This outrageous act underlines how far beyond accepted behavior the Syrian regime has put itself and I condemn it wholeheartedly," Hague said in a statement. "The Assad regime should not make the mistake of believing that it can act with impunity. It will be held to account for its behavior. The UK stands ready to pursue robust action at the United Nations Security Council."

Hague met last week with U.N and Arab League special envoy Kofi Annan for talks on plans for an international summit, while British officials discussed the issue in Geneva on Saturday with members of Annan's team.

"This deplorable incident underlines the urgent need to find a solution to the current crisis in Syria in order to bring an end to the violence and to achieve a genuine political transition," Hague said.

Davutoglu said earlier Sunday that the jet was downed in "international airspace" after it mistakenly strayed into Syria, but the plane was not on a spying mission. He said the plane had entered Syria on Friday, but quickly left when warned by Turkey.

The plane had no "covert mission related to Syria," Davutoglu said, adding that it was purely on a training flight to test Turkey's radar capabilities.

Davutoglu said the plane was shot down one mile inside the airspace several minutes after it left Syria.

Syria on Saturday insisted the shooting was "not an attack," and that the plane had violated its airspace.